Cygnus A (3C 405)

Cygnus A (3C405)

Cygnus A (3C 405) 4.8 GHz VLA map courtesy of C. Carilli.

Cygnus A (3C 405) is the strongest extragalactic radio source and third strongest radio source in the sky (after the Sun and Cassiopeiae A). At one time believed to be the result of a collision of two galaxies, it has now been identified as a classic double-lobed radio galaxy that, at optical wavelengths, is a 15th magnitude cD galaxy (a supergiant elliptical) lying about one billion light-years away in the constellation Cygnus.